U.S. patent number 4,345,714 [Application Number 06/173,894] was granted by the patent office on 1982-08-24 for control method and apparatus for air conditioners.
This patent grant is currently assigned to Nippondenso Co., Ltd.. Invention is credited to Yasuhumi Kojima.
United States Patent |
4,345,714 |
Kojima |
August 24, 1982 |
Control method and apparatus for air conditioners
Abstract
In control of an air conditioner, a first deviation
corresponding to the rate of change of the actual air temperature
in a compartment is detected such that an expected value of the
actual air temperature to be obtained as a stable value under the
control of the air conditioner is detected to detect a second
deviation in relation to a desired temperature. When the second
deviation is larger than a predetermined value, a third deviation
is also detected in relation to the second deviation to adjust the
temperature of air flow supplied from the air conditioner and to
eliminate undesired temperature deviation caused by fluctuation of
the heat load in the compartment.
Inventors: |
Kojima; Yasuhumi (Gifu,
JP) |
Assignee: |
Nippondenso Co., Ltd. (Kariya,
JP)
|
Family
ID: |
14222166 |
Appl.
No.: |
06/173,894 |
Filed: |
July 28, 1980 |
Foreign Application Priority Data
|
|
|
|
|
Aug 1, 1979 [JP] |
|
|
54-98528 |
|
Current U.S.
Class: |
236/46R; 236/91C;
165/247 |
Current CPC
Class: |
B60H
1/00807 (20130101); G05D 23/1917 (20130101); G05D
23/20 (20130101); F24F 2130/20 (20180101); F24F
2110/10 (20180101); F24F 2110/12 (20180101); F24F
11/30 (20180101) |
Current International
Class: |
B60H
1/00 (20060101); F24F 11/00 (20060101); G05D
23/20 (20060101); G05D 023/00 () |
Field of
Search: |
;62/157,231 ;165/12
;236/46R,46A,46F,46C,91R,91C |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Makay; Albert J.
Assistant Examiner: Tanner; Harry B.
Attorney, Agent or Firm: Cushman, Darby & Cushman
Claims
What is claimed is:
1. A method of controlling an air conditioner which supplies an air
flow into a compartment or other region, the air conditioner
comprising air flow quantity control means and air flow temperature
control means, the method comprising the steps of detecting the
quantity of heat necessary for adjusting the actual temperature of
air in said compartment or other region to a desired value and to
maintain it at said desired value, and controlling said air flow
temperature control means in such manner that the air flow
temperature is such as to enable the air flow at a desired air flow
quantity to supply said necessary heat quantity, said necessary
heat quantity and said air flow temperature being determined
employing electric signals in the form of a first electric signal
indicative of the actual air temperature in said compartment or
other region and a second electric signal indicative of a desired
air temperature in said compartment or other region, wherein the
improvement comprises the steps of:
detecting a first deviation between values of the preceding and
following first electric signals at a predetermined time interval
after lapse of a predetermined period of time from starting the air
conditioner;
detecting an expected value of the actual air temperature in
relation to said first deviation, said expected value of the actual
air temperature being obtained as a stable value under the control
of said air flow temperature control means;
detecting a second deviation between said desired value and said
expected value of the actual air temperature;
detecting a third deviation related to said second deviation when
said second deviation is larger than a predetermined value; and
compensating said necessary heat quantity in accordance with said
third deviation.
2. A method of controlling an air conditioner as claimed in claim
1, and comprising the step of halting the detection of said first,
second and third deviations during a predetermined period of time
after compensation of said necessary heat quantity.
3. A method of controlling an air conditioner as claimed in claim 1
or 2, wherein said first deviation is detected in response to the
preceding and following first electric signals at a time interval
of twenty seconds after lapse of two minutes from starting the air
conditioner.
4. A method of controlling an air conditioner as claimed in claim 1
or 2, wherein the step of detecting an expected value of the actual
air temperature comprises the steps of:
calculating an expected deviation related to said first deviation
based on a function defining a relationship between said first
deviation and said expected deviation; and
calculating the sum of the actual air temperature and said expected
deviation.
5. A method of controlling an air conditioner as claimed in claim 1
or 2, wherein the step of detecting an expected value of the actual
air temperature comprises the steps of:
calculating an expected deviation related to said first deviation
based on a linear function defining a relationship between said
first deviation and said expected deviation; and
calculating the sum of the actual air temperature and said expected
deviation.
6. A method of controlling an air conditioner as claimed in claim 1
or 2, wherein said third deviation is detected in relation to said
second deviation when said second deviation is larger than
0.5.degree. C.
7. In an air conditioner control apparatus for use with an air
conditioner which is arranged to supply an air flow into a
compartment or other region, such air conditioner comprising air
flow quantity control means and air flow temperature control means,
the air conditioner control apparatus being operable to control the
quantity of heat, supplied by the air conditioner, to be a quantity
necessary for adjusting the actual temperature of air in said
compartment or other region to a desired value and to maintain it
at said desired value, the air conditioner control apparatus being
operable to control said air flow temperature control means in such
manner that the air flow temperature will be such as to enable the
air flow having a desired air flow quantity to supply said
necessary heat quantity, said necessary heat quantity and said air
flow temperature being determined employing electric signals in the
form of a first electric signal indicative of the actual air
temperature in said compartment or other region, and a second
electric signal indicative of a desired air temperature in said
compartment or other region,
the improvement wherein the air conditioner control apparatus
includes means for detecting, a first deviation between values of
the preceding and following first electric signals at a
predetermined time interval after lapse of a predetermined period
of time from starting the air conditioner, and for detecting an
expected value of the actual air temperature in relation to said
first deviation, said expected value of the actual air temperature
being obtained as a stable value under the control of said air flow
temperature control means, and means for detecting a second
deviation between said desired value and said expected value of the
actual air temperature, for detecting a third deviation related to
said second deviation when said second deviation is larger than a
predetermined value, and for compensating said necessary heat
quantity in accordance with said third deviation.
8. An air conditioner control apparatus as claimed in claim 7, and
comprising a digital computer to control as aforesaid said air flow
temperature control means in dependence upon said determined values
which are calculated by the computer in accordance with its
programming.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a control method and apparatus for
air conditioners, and more particularly, but not exclusively, to a
control method and apparatus suitable for an automobile air
conditioner wherein the temperature of air flow is automatically
controlled in accordance with change of the heat load in the
passenger compartment of an automobile.
As shown in FIG. 1, a conventional control system for an air
conditioner comprises a set circuit 1 for producing an output
signal indicative of a desired temperature T.sub.set of air in a
compartment or region to be conditioned, a temperature sensor 2 for
producing an output signal indicative of the actual temperature
T.sub.r of air in the compartment, and a detector 3 responsive to
the output signals from set circuit 1 and sensor 2 for detecting
any deviation between the desired temperature T.sub.set and the
actual temperature T.sub.r and for producing an output signal
indicative of the detected deviation. A temperature controller 4
receives the output signal from detector 3 to control the
temperature of air flow in accordance with the deviation so as to
adjust the actual temperature T.sub.r to the desired temperature
T.sub.set and maintain it at the same.
During operation of temperature controller 4, the sensor 2 acts to
produce a feedback signal indicative of any change of the actual
temperature in the compartment, and the controller 4 acts to adjust
the actual temperature T.sub.r to the desired temperature T.sub.set
in response to the feedback signal from sensor 2. In this instance,
the heat load in the compartment fluctuates in accordance with
variations of the outside ambient temperature T.sub.am, and
subsequently the actual temperature T.sub.r fluctuates due to delay
of heat transfer in the compartment. To restrain fluctuation of the
actual temperature in the compartment, an outside ambient
temperature sensor 6 and an adder 7 are provided to preliminarily
compensate the fluctuation of head load caused by a change of the
outside ambient temperature T.sub.am.
In the control system described above, assuming that the quantity
of air flow is at a constant value, the temperature of air flow is
adjusted by controller 4 as represented by the following
equation.
where T.sub.set is the desired temperature in the compartment,
T.sub.am is the outside ambient temperature, T.sub.r is the actual
temperature in the compartment, C is a constant, and K.sub.set,
K.sub.am and K.sub.r are respectively gains of set circuit 1 and
sensors 6 and 2, which are preliminarily determined to adjust the
actual temperature T.sub.r toward the desired temperature T.sub.set
without any influence caused by changes of the outside ambient
temperature. In controlling the air conditioner, although the
outside ambient temperature is measured to compensate the
temperature of air flow in accordance with fluctuation of the heat
load in the compartment, it is disregarded to compensate the
temperature of air flow in relation to another fluctuation of the
heat load caused by the intensity and direction of sunshine
entering the compartment, change of the vehicle speed and the
number of passengers and the like, since the constant C is
experimentarily determined in a fixed value. This results in any
deviation between the actual temperature and the desired
temperature due to the disregarded fluctuation of the heat
load.
SUMMARY OF THE INVENTION
It is, therefore, the primary object of the present invention to
provide an improved method and apparatus of controlling an air
conditioner in which the rate of change of the actual air
temperature in the compartment to be conditioned is detected at a
predetermined time interval after lapse of a predetermined period
of time from starting the air conditioner to preliminarily measure
an expected value of the actual air temperature to be obtained as a
stable value under control of the air conditioner, and in which the
quantity of heat supplied by the air conditioner is compensated in
accordance with a deviation between a desired air temperature and
the expected value of the actual air temperature to eliminate
undesired temperature deviation caused by the disregarded
fluctuation of the heat load in the compartment.
According to an aspect, the present invention is directed to
improve a method of controlling an air conditioner which supplies
an air flow into a compartment or other region, the air conditioner
comprising an air flow quantity control device and an air flow
temperature control device, the method comprising the steps of
detecting the quantity of heat necessary for adjusting the actual
temperature of air in the compartment or other region to a desired
value and to maintain it at the desired value, and controlling the
air flow temperature control device in such manner that the air
flow temperature is such as to enable the air flow at a desired air
flow quantity to supply the necessary heat quantity, the necessary
heat quantity and the air flow temperature being determined
employing electric signals in the form of a first electric signal
indicative of the actual air temperature in the compartment or
other region and a second electric signal indicative of a desired
air temperature in the compartment or other region.
The improvement of the method comprises the steps of;
detecting a first deviation between values of the preceding and
following first electric signals at a predetermined time interval
after lapse of a predetermined period of time from starting the air
conditioner;
detecting an expected value of the actual air temperature in
relation to the first deviation, the expected value of the actual
air temperature being obtained as a stable value under the control
of the air flow temperature control device;
detecting a second deviation between the desired value and the
expected value of the actual air temperature;
detecting a third deviation related to the second deviation when
the second deviation is larger than a predetermined value; and
compensating the necessary heat quantity in accordance with the
third deviation.
According to another aspect, the present invention is directed to
improve an air conditioner control apparatus for use with an air
conditioner which is arranged to supply an air flow into a
compartment or other region, such air conditioner comprising an air
flow quantity control device and an air flow temperature control
device, the air conditioner control apparatus being operable to
control the quantity of heat, supplied by the air conditioner, to
be a quantity necessary for adjusting the actual temperature of air
in the compartment or other region to a desired value and to
maintain it as the desired value, the air conditioner control
apparatus being operable to control the air flow temperature
control device in such manner that the air flow temperature will be
such as to enable the air flow having a desired air flow quantity
to supply the necessary heat quantity, the necessary heat quantity
and the air flow temperature being determined employing electric
signals in the form of a first electric signal indicative of the
actual air temperature in the compartment or other region, and a
second electric signal indicative of a desired air temperature in
the compartment or other region.
The improvement of the present invention is characterized in that
the air conditioner control apparatus is operable to detect a first
deviation between values of the preceding and following first
electric signals at a predetermined time interval after lapse of a
predetermined period of time from starting the air conditioner and
to detect an expected value of the actual air temperature in
relation to the first deviation, the expected value of the actual
air temperature being obtained as a stable value under the control
of the air flow temperature control device, and that the air
conditioner control apparatus is operable to detect a second
deviation between the desired value and the expected value of the
actual air temperature so as to detect a third deviation related to
the second deviation when the second deviation is larger than a
predetermined value thereby to compensate the necessary heat
quantity in accordance with the third deviation.
BRIEF DESCRIPTION OF THE DRAWINGS
Additional objects and advantages of the present invention will be
more readily apparent from the following detailed description of a
preferred embodiment thereof when taken together with the
accompanying drawings in which:
FIG. 1 is a functional block diagram of a conventional air
conditioner control system.
FIG. 2 is a schematic block diagram of an air conditioner control
apparatus in accordance with the present invention adapted to an
automobile air conditioner;
FIG. 3 is a flow diagram illustrating operation of the
microcomputer shown in block form in FIG. 2;
FIG. 4 is a graph illustrating the rate of change of the actual
temperature of air in the compartment under control of the air
conditioner; and
FIG. 5 is a graph illustrating an expected deviation related to the
rate of change of the actual temperature of air.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 2 of the drawings, there is schematically
illustrated a preferred embodiment of the present invention in
which a microcomputer 21 is utilized to execute a predetermined
computer program for air conditioning in the passenger compartment
of a vehicle. The reference numeral 10 indicates an air duct of a
conventional automobile air conditioner which is provided therein
with a blower 11, a cooler-core 12, and a heater-core 13. The air
duct 10 is located at the front portion of the passenger
compartment. An air-blend door 14 is arranged in a conventional
manner to adjust the proportion of the cooled air from cooler-core
12 and the warmed air from heater-core 13 flowing into the
passenger compartment, as shown by an arrow in the figure. The
microcomputer 21 is connected through an analog-to-digital or A-D
converter 20 to an in-car temperature sensor 15, an outside ambient
temperature sensor 16, a sunshine sensor 17, a temperature setting
circuit 18, and an air flow setting circuit 19.
The in-car temperature sensor 15 is located in the shade of the
passenger compartment under an instrument panel of the vehicle to
detect actual average in-car temperature in the compartment and to
produce an electric signal indicative of the actual in-car
temperature T.sub.r'. The outside ambient temperature sensor 16 is
located outside the passenger compartment to detect actual outside
ambient temperature and to produce an electric signal indicative of
the actual outside temperature T.sub.am'. The sunshine sensor 17 is
located inside the passenger compartment to detect intensity of
sunshine and to produce an electric signal indicative of the
intensity of sunshine T.sub.s'. The temperature setting circuit 18
includes a variable resistor which is manually adjusted to produce
an electric signal indicative of a desired in-car temperature
T.sub.set'. The air flow setting circuit 19 is provided to produce
an electric signal indicative of a desired quantity of air flow W.
A-D converter 20 acts to convert the electric signals from sensors
15 to 19 into electric binary signals respectively.
The microcomputer 21 is in the form of a single chip LSI
microcomputer which receives a constant voltage from a voltage
stabilizer (not shown) in its operation. The voltage stabilizer is
supplied with electric power from a vehicle battery (not shown)
upon closing an ignition switch (not shown) to produce the constant
voltage therefrom. The microcomputer 21 comprises a central
processing unit or CPU which is connected to an input-output device
or I/O through a bus line 21a. CPU is also connected through bus
line 21a to a clock circuit, a read only memory or ROM and a random
access memory or RAM. I/O receives the electric binary signals from
A-D converter 20 to store them in RAM temporarily. These stored
signals are selectively read out from RAM and applied to CPU
through bus line 21a. CPU serves to execute the predetermined
computer program in accordance with clock signals from the clock
circuit. The clock circuit is cooperable with a crystal oscillator
22 to produce the clock signals at a predetermined frequency. The
predetermined computer program is stored in ROM such that the
computer 21 calculates the quantity of heat necessary for
controlling the in-car temperature at a desired level and
calculates the temperature of air flow T.sub.ao necessary for
discharging the calculated quantity of heat by a predetermined
quantity of air flow W into the passenger compartment, as described
in detail later.
A first driving circuit 23 has an input terminal connected to a
first output terminal of computer 21 and an output terminal
connected to an input terminal of blower 11. The first driving
circuit 23 acts to conduct a chopper control of blower 11 in
response to an output signal indicative of a predetermined quantity
of air flow from computer 21 under control of the air flow setting
circuit 19. Thus, the blower 11 is driven to supply the
predetermined quantity of air flow into the passenger compartment
in accordance with setting of the air flow setting circuit 19. An
electrically operated actuator 25 is in the form of an electric
motor or an electromagnetically operated servomotor which is linked
with air-blend door 14 to control the angular position of blend
door 14 in response to an output signal from a second driving
circuit 24. The second driving circuit 24 has an input terminal
connected to a second output terminal of computer 21 and an output
terminal connected to an input terminal of actuator 25. The second
driving circuit 24 acts to control electric power supply to
actuator 25 in response to an output signal indicative of the
calculated temperature of air flow from computer 21. Thus, the
angular position of air-blend door 14 is adjusted by operation of
the actuator 25 to maintain the temperature of air flow discharged
from the air conditioner in the calculated resultant value. In
addition, the second driving circuit includes a position sensor
(not shown) which is provided to detect the angular position of
air-blend door 14 for detecting the actual temperature of air flow
from the air conditioner.
Hereinafter, operational modes of the above control system will be
described in detail with reference to a flow chart shown in FIG. 3.
When the voltage stabilizer is energized by closing the ignition
switch to produce a constant voltage therefrom, the microcomputer
21 is conditioned in its operation to initiate execution of the
following calculations according to the predetermined program at a
frequency of approximately several milliseconds. Simultaneously,
electric signals from sensors 15, 16 and 17 and setting circuits 18
and 19 are converted by A-D converter 20 into binary signals
respectively indicative of actual in-car temperature T.sub.r,
outside ambient temperature T.sub.am, intensity of sunshine
T.sub.s, a desired in-car temperature T.sub.set and a desired
quantity of air flow W. When the computer program proceeds to a
point 101, the binary signals from A-D converter 20 are memorized
in RAM of computer 21. At a point 102, CPU of computer 21 proceeds
the program to a point 106 through a routine including points 103,
104 and 105 at the first stage immediately after the initiation of
calculation. Then, CPU of computer 21 acts at point 103 to start a
first timer T.sub.1 associated therewith, and acts respectively at
points 104 and 105 to set .DELTA.T.sub.set =0, .DELTA.T.sub.setN =0
and N=1, where .DELTA.T.sub.set is a deviation between a desired
value and an expected value of the actual in-car temperature to be
obtained as a stable value under control of the air conditioner,
.DELTA.T.sub.setN is a previously calculated deviation of
.DELTA.T.sub.set, and N is a flag.
At point 106, CPU of computer 21 calculates a quantity of heat Q to
be supplied into the passenger compartment, which may correspond
with change of the heat load in the compartment. For instance,
assuming that the quantity of air flow W is at a value W.sub.o, a
temperature of air flow T.sub.aoo is calculated from the following
equation.
where T.sub.set is the desired in-car temperature, T.sub.am is the
outside ambient temperature, T.sub.r is the actual in-car
temperature, C is a constant, and K.sub.set, K.sub.am and K.sub.r
are respectively gains of set circuit 18 and sensors 16, 15. Based
on the above calculation, the quantity of heat Q is calculated by
CPU of computer 21 from the following equation.
where K.sub.q is a constant determined by the physical property of
air. Then, CPU of computer 21 calculates a temperature of air flow
T.sub.ao necessary for discharging the calculated quantity of heat
Q at a predetermined quantity of air flow W. The calculation of
temperature T.sub.ao is executed by CPU of computer 21 based on the
following equation.
At point 123, CPU of computer 21 produces output signals
respectively indicative of the predetermined quantity of air flow W
and the calculated temperature T.sub.ao of air flow, each of which
is applied to the first and second driving circuits 23 and 24.
When the computer program is returned to point 102 after the first
calculation, as described above, the program proceeds to point 107
where CPU of computer 21 discriminates as to whether or not one
hundred seconds lapse from the start of timer T.sub.1. If an answer
is "no", CPU proceeds the computer program to point 106 to
calculate a temperature of air flow T.sub.ao as same as the first
calculation. Subsequently, at point 123 CPU of computer 21 produces
output signals respectively indicative of the predetermined
quantity of air flow W and the calculated temperature of air flow
T.sub.ao, as previously described. If the answer at point 107 is
"yes", CPU of computer 21 proceeds the program to a point 108 to
discriminate whether or not the flag is zero. In this instance, CPU
of computer 21 discriminates as 37 yes" because the flag is
preliminarily set as N=0 at point 105, and it proceeds the program
to a point 109 to start a second timer T.sub.2 associated with CPU.
Subsequently, a reference in-car temperature T.sub.ro is set at a
point 110 as the actual in-car temperature T.sub.r newly read out
from RAM, and at point 111 the flag is set as N=0. The flag N is
used to execute a routine including points 113 to 122 at a time
interval of twenty seconds, as described in detail later.
When the computer program is returned to point 108 through points
106, 123, 101, 102 and 107, CPU of computer 21 discriminates as
"yes" because the flag N is previously set as zero at point 111,
and it proceeds the program to a point 112 to discriminates as to
whether or not twenty seconds lapse after the start of second timer
T.sub.2. If an answer is "no" at point 112, CPU of computer 21
proceeds the program to perform the calculations at point 106, as
described above. If the answer is "yes" at point 112, CPU of
computer 21 proceeds the program to the routine including points
113 to 122. In this routine, CPU of computer 21 acts to detect a
first deviation between the reference in-car temperature T.sub.ro
and the actual in-car temperature T.sub.r at the time interval of
twenty seconds so as to detect an expected value of the actual
in-car temperature in relation to the first deviation to be
obtained as a stable value under the control of the air
conditioner, and CPU of computer 21 further acts to detect a second
deviation between the desired in-car temperature and the expected
value of the actual in-car temperature so as to detect a third
deviation related to the second deviation when the second deviation
is equal to or larger than 0.5.degree. C., thereby compensating the
necessary heat quantity in accordance with the third deviation, as
described in detail hereinafter.
At point 113, CPU of computer 21 calculates a deviation DT between
the reference in-car temperature T.sub.ro and the actual in-car
temperature T.sub.r based on an equation of DT=T.sub.r -T.sub.ro to
detect the rate of change of the actual in-car temperature under
control of the air conditioner. At point 114, CPU of computer 21
calculates an expected deviation in relation to the calculated
deviation DT based on a function of T.sub.rf =f(DT). In this case,
the function of T.sub.rf =f(DT) is experimentally obtainable taking
into consideration capability of the air conditioner, capacity of
the passenger compartment and the like. In addition, the function
of T.sub.rf =f(DT) may be replaced with an appropriate linear
function in the form of T.sub.rf =a.multidot.DT where a is a
constant. Subsequently, the program proceeds to point 115 where CPU
of computer 21 calculates the sum of the expected deviation
T.sub.rf and the actual in-car temperature T.sub.r based on an
equation of T.sub.setf =T.sub.r +T.sub.rf thereby to detect an
expected value of the actual in-car temperature T.sub.r to be
obtained as a stable value under the control of the air
conditioner.
At point 116, CPU of computer 21 calculates a deviation
.DELTA.T.sub.set between the desired in-car temperature T.sub.set
and the expected value T.sub.setf of the actual in-car temperature
based on an equation of .DELTA.T.sub.set =T.sub.set -T.sub.setf.
Subsequently, the program proceeds to point 117 where CPU of
computer 21 discriminates as to whether or not an absolute value of
the calculated deviation .DELTA.T.sub.set is equal to or larger
than 0.5.degree. C. If answer is "no", CPU of computer 21 proceeds
the program to point 118 to set the deviation .DELTA.T.sub.set as
null, and it acts to halt operation of first timer T.sub.1 at point
119. This means that the first timer T.sub.1 is stopped upon lapse
of two minutes from its starting operation.
When the program proceeds to point 121, CPU of computer 21 acts to
set the flag as N=1 to repetitively perform the discrimination at
point 117 at a time interval of twenty seconds, as previously
described. If the answer is "yes", the program proceeds to point
120 where CPU of computer 21 acts to restart the first timer
T.sub.1 from its zero second. Subsequently, CPU of computer 21 acts
at point 121 to set the flag as N=1 and at point 122 to calculate a
deviation .DELTA.T.sub.setN based on the following equation.
where .DELTA.T.sub.setN is a previously calculated value and
.DELTA.T.sub.set is a successively calculated value.
Upon completion of the calculation at point 122, the calculated
deviation .DELTA.T.sub.setN is entered into the calculation of the
above-noted equation (1) to compensate the value of heat quantity
calculated at point 106. As a result, the temperature T.sub.ao of
air flow is compensated in accordance with the calculated deviation
.DELTA.T.sub.setN to reliably direct the actual in-car temperature
T.sub.r toward the desired value T.sub.set. Sequentially, CPU of
computer 21 returns the program to point 101 through point 123 to
halt the calculation at points 113 to 122 within two minutes after
start of the first timer T.sub.1 at point 120.
In FIG. 4, there is illustrated the actual in-car temperature
T.sub.r in relation to lapse of time t during operation of the air
conditioner control apparatus. Assuming that CPU of computer 21
initiates execution of the computer program to adjust the actual
in-car temperature to a desired temperature T.sub.set of 25.degree.
C. in summer, control of the actual in-car temperature in the
compartment is continued without execution at points 120, 122
within two minutes after start of the program, as shown at points
101 to 112 of FIG. 3. If the actual in-car temperature T.sub.r is
stabilized by 2.degree. C. higher than the desired temperature
T.sub.set under control of the air conditioner, as shown by a curve
b in FIG. 4, a deviation DT.sub.1 will be calculated at point 113
after lapse of two minutes, as shown at a timing A in FIG. 4. Then,
at point 114 a deviation T.sub.rf will be calculated as -3.degree.
C. in relation to the calculated deviation DT.sub.1, as shown in
FIG. 5. If the actual in-car temperature T.sub. r is 30.degree. C.
at the timing A of FIG. 4, a value of T.sub.setf will be calculated
as 27.degree. C. at point 115 in relation to the calculated
deviation T.sub.rf. At point 116, a deviation .DELTA.T.sub.set will
be obtained as -2.degree. C. in relation to the desired value
T.sub.set and the calculated value T.sub.setf.
When CPU of computer 21 discriminates at point 117 that an absolute
value of the deviation .DELTA.T.sub.set =-2.degree. C. exceeds
0.5.degree. C., the first timer T.sub.1 is restarted at point 120,
and a deviation .DELTA.T.sub.setN is calculated at point 122 as
-2.degree. C. in relation to the initial value .DELTA.T.sub.setN =0
and the deviation .DELTA.T.sub.set =-2.degree. C. Thus, a necessary
heat quantity is calculated in relation to the deviation
.DELTA.T.sub.setN =-2.degree. C. to direct the actual in-car
temperature T.sub.r toward the desired temperature of 25.degree. C.
In addition, until lapse of two minutes defined by timings A and B
in FIG. 4, a necessary heat quantity is repetitively calculated in
relation to the deviation .DELTA.T.sub.setN =-2.degree. C., as
previously described, to direct the actual in-car temperature
toward the desired temperature of 25.degree. C.
Upon lapse of two minutes defined by the timings A, B of FIG. 4,
CPU of computer 21 calculates a deviation .DELTA.T.sub.set at point
116 to discriminate whether or not an absolute value of the
deviation .DELTA.T.sub.set is equal to or larger than 0.5.degree.
C., as previously described. If an answer is "no" at point 117
because of no change of the heat load in the compartment, CPU of
computer 21 acts to set the deviation .DELTA.T.sub.set as zero at
point 118 to halt operation of the first timer T.sub.1 at point
119. Thereafter, the computer program is returned to point 102
through points 121, 106, and 123 to discriminate at a time interval
of twenty minutes as to whether or not execution at points 113 to
117 should be performed.
Assuming that the number of passengers is decreased upon lapse of
ten minutes defined by a timing C in FIG. 4 and that the actual
in-car temperature is stabilized at an expected value of 24.degree.
C., the computer program proceeds to point 113 to calculate a
deviation DT.sub.2 from the equation of DT=T.sub.r -T.sub.ro, as
previously described. Then, CPU of computer 21 calculates a
deviation T.sub.rf as -1.degree. C. at point 114 in relation to the
deviation DT.sub.2, as shown in FIG. 5, and also calculates a value
T.sub.setf as 24.degree. C. in relation to the deviation T.sub.rf
of -1.degree. C. and the desired temperature T.sub.set of
25.degree. C. When a deviation .DELTA.T.sub.set is calculated as
1.degree. C. at point 116 in relation to the desired and calculated
values T.sub.set of 25.degree. C. and T.sub.setf of 24.degree. C.,
CPU of computer 21 discriminates as "yes" at point 117 to restart
the timer T.sub.1 at point 120. Then, CPU of computer 21 calculates
a deviation .DELTA.T.sub.setN at point 122 in relation to the
previously calculated value .DELTA.T.sub.setN and the deviation
.DELTA.T.sub.set of 1.degree. C. Thereafter, CPU also calculates a
necessary heat quantity in relation to the calculated deviation
.DELTA.T.sub.setN at point 106 to adjust the actual in-car
temperature from 24.degree. C. toward 25.degree. C. As a result,
the actual in-car temperature is smoothly adjusted by the air
conditioner control apparatus within a predetermined range between
(T.sub.set +0.5.degree. C.) and (T.sub.set -0.5.degree. C.).
Additionally, each time interval defined by timers T.sub.l, T.sub.2
may be modified in accordance with capability of the air
conditioner to effectively prevent the computer from its hunting
operation to be caused by various disturbances.
In the actual practices of the present invention, the above air
conditioner control apparatus may be modified to eliminate both of
the ambient and sunshine sensors 16, 17. Thus, the modified control
apparatus becomes simple in construction and low in production
cost. The modified control apparatus also ensures substantially the
same precise control as that of the above embodiment. In this
modification, the actual in-car temperature may be adjusted in
combination of each control of the air blend door 14 and blower
11.
Although a certain specific embodiment of the present invention has
been shown and described, it is obvious that many modifications and
variations thereof are possible in light of these teachings. It is
to be understood therefore that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
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